Human-Induced Changes on Biogeochemical Cycles

1. The Carbon Cycle
This process is focused on carbon, which makes up 0.038% of the atmosphere as a gas. This cycle is the global movement of carbon between organisms and the abiotic environment, including the atmosphere, the ocean, and sedimentary rock. Through the process of photosynthesis, CO2 is removed from the air and incorporated into chemical compounds like sugar, which plants use to make other compounds. These compounds are then used as fuel for cellular respiration by the producer that created them. Through the trophic levels by having consumers eat the producers and decomposers that break down their remains, CO2 is returned into the atmosphere.

As a species, we have been altering this cycle ever since the Industrial Revolution in 1750. Disturbing the balance of the cycle, we have been using up a ton of energy in the atmosphere, which we have obtained by burning various amounts of fossil fuels such as oil, coal, and natural gasses, and our need for these resources is expanding as fast as we harvest them. This has made large amounts of carbon release itself upon the atmosphere, rising higher and higher in percentage. Eventually, it will increase so much that the global climate levels will change drastically.



2. The Nitrogen Cycle
This process is when nitrogen moves between the abiotic environment and organisms. It contains five different steps in it's process. The first step is nitrogen fixation, the conversion of gaseous nitrogen to ammonia NH3, a form that organisms can use. Next comes nitrification, the conversion of ammonia NH3 to nitrite NO2, which the soil then takes and oxidizes to form nitrate NO3. Next is assimilation, where the plant roots absorb the nitrate and incorporate the nitrogen of the molecules to plant proteins and nucleic acids which the animals then assimilate by taking in nitrogen compounds. The fourth process is ammonification, the conversion of biological nitrogen compounds into ammonia NH3, and dentrification, the final process, is the reduction of that nitrate to gaseous nitrogen, which precipitation washes away into rivers, lakes and coastal areas.

Human beings consume fossil fuels and burn them, releasing high temperatures of combustion which convert atmospheric nitrogen into nitrogen oxides. This produces photochemical smog, a mixture of air pollutants that kills off plants and causes breathing problems for people.there is also acid deposition left in the water and that causes the pH of surface water to decrease, therefore altering soil chemistry on land.


3. The Phosphorus Cycle
In this cycle, phosphorus moves from the land to sediments in the ocean and back again. The erosion of minerals that contain phosphorus into the soil and plants incorporate that into biological molecules such as nucleic acids and ATP. This is taken in by animals, and the decomposers then release phosphorus back into the soil for plants to reuse.

Humans affect the phosphorus cycle by accelerating long-term loss effects of phosphorus on the land. This means that they consume more phosphorus than natural beings would, creating human wastes that are flushed into sewer systems, thereby causing problems in water quality in rivers, lakes, and coastal areas. This kind of phosphorus is permanently lost from the terrestrial phosphorus cycle, and from further use by anyone including humans. This can lead to undesirable changes in the water quality.


4. The Sulfur Cycle
We are still not exactly sure how this one works, but what we have so far is that sulfur, underground in sedimentary rocks and minerals, erode to release compounds that contain sulfur into the ocean. Sulfur gas then enters the atmosphere from natural sources both in the ocean and on land, which sea spray, forest fires and other natural causes deliver the sulfides into the air.

The human population runs on fuels such as coal and oil, and both of these products contain sulfur. When these things are burned in power plants, factories and otherwise, the sulfur oxide is released into the atmosphere. This can be a major cause of acid deposition and global emissions. 

5. The Hydrologic (Water) Cycle
This is a very important process, since it involves water, a necessary ingredient in all forms of life. In it, water continuously circulates from the ocean to the atmosphere to the land and back to the ocean, providing a renewable supply of purified water. Water moves from the air to the land through precipitation, and eventually moves back from land and reenters the atmosphere again through evaporation. There is also the process of transpiration, the loss of water vapor from land plants, which adds water to the atmosphere.

Thanks to mankind, our increased air pollution also affects the water. Every time we release sulfates, nitrates, carbon, mineral dusts and other waste products into the air, that forms tiny particles of air pollution called Aerosols, which seem affect the sunlight and forms clouds, which in term affect the quality of water in some regions of the world and altering their evaporation levels.